One thousand nine hundred and fifty-three non-invasive breast cancers were diagnosed by the National Health Service Breast Screening Programme (NHSBSP) in women aged 50–64 during the period 1999–2000. Prior to the introduction of screening only 295 cases of ductal carcinoma in situ (DCIS) were recorded in England and Wales in women in the same age band. The reason for this is that the trademark characteristic of microcalcification in the majority of DCIS cases is easily visualised radiologically on a mammogram. Consequently, with the introduction of breast screening, the incidence of this type of cancer has been increasing rapidly, and DCIS now accounts for approximately 20% of all cancers detected by the NHSBSP.

The invasive potential of each DCIS is uncertain and accordingly the optimal method of treatment in every case is unclear. The Sloane Project aims to address this question. As a prospective audit recording particular characteristics in terms of radiological and pathological appearance and details of surgical and adjuvant treatment, the audit will compile a database of potentially 6,000 DCIS cancers over 3 years. These women will be followed up and the incidence of local recurrence, metastases and deaths will be determined. This information will allow us to calculate survival, to suggest what might be the optimal treatment for DCIS, to identify prognostic indicators and to examine the role of margins and adjuvant therapy on outcome.